<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<html>
<head>
<!-- Copyright 1997 The Open Group, All Rights Reserved -->
<title>setvbuf</title>
</head><body bgcolor=white>
<center>
<font size=2>
The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

</font></center><hr size=2 noshade>
<h4><a name = "tag_000_008_516">&nbsp;</a>NAME</h4><blockquote>
setvbuf - assign buffering to a stream
</blockquote><h4><a name = "tag_000_008_517">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="stdio.h.html">stdio.h</a>&gt;

int setvbuf(FILE *<i>stream</i>, char *<i>buf</i>, int <i>type</i>, size_t <i>size</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_008_518">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>setvbuf()</i>
function may be used after the stream pointed to by
<i>stream</i>
is associated with an open file but before any other
operation is performed on the stream.
The argument
<i>type</i>
determines how
<i>stream</i>
will be buffered, as follows:
_IOFBF causes input/output to be fully buffered;
_IOLBF causes input/output to be line buffered;
_IONBF causes input/output to be unbuffered.
If
<i>buf</i>
is not a null pointer, the array it points to may be used instead
of a buffer allocated by
<i>setvbuf()</i>.
The argument
<i>size</i>
specifies the size of the array.
The contents of the array at any time are indeterminate.
<p>
For information about streams, see
<a href="stdio.html">Standard I/O Streans</a>.
</blockquote><h4><a name = "tag_000_008_519">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion,
<i>setvbuf()</i>
returns 0.  Otherwise, it returns a non-zero value if an invalid value is
given for
<i>type</i>
or if the request cannot be honoured.
</blockquote><h4><a name = "tag_000_008_520">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>setvbuf()</i>
function may fail if:
<dl compact>

<dt>[EBADF]<dd>
The file descriptor underlying
<i>stream</i>
is not valid.

</dl>
</blockquote><h4><a name = "tag_000_008_521">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_522">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
A common source of error is allocating buffer space
as an &quot;automatic&quot; variable in a code block, and then
failing to close the stream in the same block.
<p>
With
<i>setvbuf()</i>,
allocating a buffer of
<i>size</i>
bytes does not necessarily imply that all of
<i>size</i>
bytes are used for the buffer area.
<p>
Applications should note that many implementations only provide line
buffering on input from terminal devices.
</blockquote><h4><a name = "tag_000_008_523">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_524">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="fopen.html">fopen()</a></i>,
<i><a href="setbuf.html">setbuf()</a></i>,
<i><a href="stdio.h.html">&lt;stdio.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from Issue 1 of the SVID.
</blockquote><hr size=2 noshade>
<center><font size=2>
UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
<br> [ <a href="../index.html">Main Index</a> | <a href="../xshix.html">XSH</a> | <a href="../xcuix.html">XCU</a> | <a href="../xbdix.html">XBD</a> | <a href="../cursesix.html">XCURSES</a> | <a href="../xnsix.html">XNS</a> ]

</font></center><hr size=2 noshade>
</body></html>

